1. Field of the Invention
The present invention relates generally to the field of fiber optics and, more particularly, to a hermetically sealed fiber optic splice closure assembly. Assemblies of the type under consideration are particularly suited for enclosing and housing fiber optic cables in aerial, pedestal, below grade, or buried applications.
2. Description of the Related Art
Fiber optic splice closures are generally required to retain fiber optic cables firmly in position such that the optical fibers contained within the cables may be joined at splice junctions such as fusion welds within splice trays supported within the closure assembly. Generally it is required that the closure assembly be hermetically sealed and that the entry locations of the fiber optic cables into the closure assembly also be hermetically sealed and water resistant.
One problem which is generally encountered in attaching the cables with respect to the closure assembly is that water-resistant conditions generally require relatively rigid connections between the closure assembly and the cables, thus presenting the possibility of applying substantial forces to the cable which may cause deformation or strain to the cable. Furthermore, when the cable enters the closure assembly, the individual splice trays are intended to retain the individual delicate optical fibers emanating from the cables in a manner which does not deform the fibers.
As noted, the splice trays are intended to retain the delicate optical fibers in position without distorting the fibers or the spliced fusion welds. In order to service the system, it is generally required to lift the individual splice trays away from one another to perform service on the cables and the fibers. In general, the fibers within the tray are provided with excessive footage to permit separable movement of the trays relative to each other to permit servicing crews to perform tasks on the fibers.
We have invented a closure assembly which provides unique water-resistant attachment of the cables thereto without subjecting the cables of the optical fibers therein to strain in causing stresses. Moreover, we have invented unique fiber optic trays capable of supporting the fibers with ready removal and reinsertion capability, while also providing pivotal attachment capability of the trays at both ends.
The illustrated embodiment of the optical splice closure assembly is for an in-line splice. However, as would be readily understood by those skilled in the art, the features of the present invention may also be similarly and beneficially applied to a butt-splice. The closure assembly is hermetically sealed and remains air-tight to prevent water from entering the case.
The optical splice closure assembly according to the invention includes a housing assembly which houses and encloses a splice tray support assembly. The housing assembly is generally formed by a pair of closely similar, opposed main housing or body members which are joined together in sealed relationship to define an axially elongated generally cylindrical center storage chamber. The opposite ends of the housing members are respectively closed by end plate assemblies that are releasably and sealingly engaged with the housing members in a manner shown in the drawings and subsequently described. The end plate assemblies are preferably made of a durable rigid material such as aluminum. One or more fiber optic cables may enter and exit the housing assembly through suitable openings in the end plate assemblies. The fiber optic cables are sealed and secured within the housing assembly by the end plate assemblies.
Although the housing body components and the end plates could be formed from a variety of different materials using different manufacturing techniques, in the embodiment shown, they are preferably injection molded from a durable glass-filled high-density thermoplastic.
The two main housing members are closely similar in overall shape and construction. Accordingly, a description of one is to be considered as equally applicable to the other unless otherwise noted. In the preferred embodiment shown in the drawings, each housing member has an elongated, semi-cylindrical configuration which defines a somewhat shell-like body with a main outer semi-cylindrical wall that has laterally extending clamping flanges extending along each longitudinal side. The flanges are in diametrical alignment relative to the wall and define flat sealing and clamping surfaces that are continuous along each side.
The main wall is reinforced by radially extending, axially spaced ribs formed integrally with the wall. Each of the ribs extends circumferentially about the wall and joins at its ends with the clamping flanges.
The clamping together of the main body components may be accomplished with a variety of different releasable fasteners or clamping means. In the subject embodiment, however, the preferred form comprises a plurality of threaded bolt members extending through associated openings in the clamping flanges and secured by corresponding nut members. The two main housing member halves may thus be clamped together by the nut and bolt members. The actual clamping and sealing arrangement will subsequently be described.
The longitudinally spaced axial ends of each of the body members are provided with an inwardly extending end flange section having a central groove/recess configured and sized so as to receive the outer peripheral edge of the associated end plate assemblies. Similarly, the clamping flanges include associated grooves/recesses in communication with the grooves/recesses in the end flange sections. Associated with the recesses and the longitudinally extending clamping surfaces of the clamping flanges on each of the housing members is a resilient sealing gasket member. The gaskets are bonded into position in each of the main body members. The gasket members used in the subject embodiment generally comprise semi-cylindrical end portions spaced and contoured to fit within the spaced recesses. The arcuate semi-cylindrical end portions are joined by relatively narrow longitudinally extending strips. Note that the strips run closely adjacent the inner periphery of the wall and the accurate end portions extend into the associated recesses.
It should be understood that the end plate assemblies are sized and shaped so as to be closely and tightly received in the recesses so as to be sealingly engaged about their outer periphery by the associated gasket portions in the bottom of the recesses. The end plate assemblies are preferably molded from the same material as the main body sections. They have a circular outer periphery of an axial width to be closely received in the recesses. The assemblies are preferably comprised of three separate pieces comprised of a central section and duplicate outer sections which fit together to provide a continuous outer periphery having a plurality of outwardly extending sealing ribs formed thereabout. The ribs are arranged to sealingly engage the gasket portion located in the bottom of the recess in the end flange section. The three separate pieces of the end plate assemblies allow the closure assembly to be disassembled without cutting or disturbing the fiber optic cable as well as allows the cables to be placed in position prior to joining the end plate members. All components used in constructing the closure assembly may be removed including any grommets or sealants directly on the cable. The central and outer sections of the end plate assemblies are each joined by a pair of bolts extending through vertically aligned openings.
Suitable cable openings are formed centrally of the end plate assemblies and any desired number of sizes could be provided. In the preferred embodiment, there are four cable openings. Those openings which are not utilized may be sealed by using suitable plugs.
In order to provide strain relief, two washer halves are provided having fingers which extend around and clamp the cable entering the closure assembly. The fingers have a gripping surface that faces the cable. A lip is provided on the outside external edge to locate the band/hose clamp and keep it from sliding off of the fingers. The strain relief washers prevent the cable from movement side-to-side due to a bending force and from axial movement when the cable is moved along the cable direction.
Two strain relief washers are used on each cable entering the closure assembly, one of the outside and one on the inside. The outside washer edges fit into corresponding grooves in the end plate assemblies. Once in place, when the band clamps are tightened, the washer edges are forced to deflect inside the groove causing additional movement resistance and xe2x80x9clockingxe2x80x9d the cable in place in the endplate. A flat or bump may be added to the washer to fit against a corresponding feature in the groove to prevent the cable from twisting or torsion movement.
It should also be noted that, in a preferred embodiment, each opening in the end plate assemblies has a cable strength member bracket located inside the closure to secure elongated wire-like strength member of the cables.
Broadly stated, the invention is directed to an enclosure for supporting at least one fiber optic cable, which comprises a housing having first and second end portions, at least one end plate located at each end portion, each end plate defining at least one aperture for supporting at least one fiber optic cable extending therethrough. The invention further comprises a device for gripping the at least one fiber optic cable adjacent at least one of the end plates, the gripping device substantially encircling the cable and having at least one extension adapted for attachment to the at least one end plate to fix the axial position of the at least one cable gripped thereby.
The invention also relates to a splice tray for supporting optical fibers, which comprises a tray for supporting the optical fibers in an axial direction, and a tray-to-tray connecting device located at each end of the tray, each connecting device being comprised of at least one elongated generally cylindrical member positioned adjacent at least one clamp member adapted to engagingly receive in clamped relation, one of such cylindrical members attached to an adjacent similar tray in a manner to permit relative pivotal movement therebetween, such that at least two of such trays may be stacked in connected relation whereby the trays may be pivotally rotated with respect to each other from either end.
The invention also relates to a device for supporting a fiber optic cable with respect to an enclosure, the enclosure having a housing having at least two end portions, and an end plate at each end portion defining at least one aperture for reception of the fiber optic cable, which comprises a gripping device structured to substantially encircle the cable at a location adjacent at least one of the end plates, the gripping device having at least two gripping members adapted to move toward and away from an outer surface portion of the cable between positions whereby the cable is gripped and released, respectively. A member, preferably in the shape of a split washer, extends generally radially from the gripping device at at least one end portion thereof, the member adapted to be fixedly attached to the end plate, and an encircling member adapted to encircle the gripping device and to selectively apply inward force to said gripping device to cause the gripping device to grip the cable.